This invention relates to an ignition device, and in particular, to an ignition device having safety features, for use in an instant heating container for promptly heating water, oil or other liquids, or solids, and which is especially suitable for outdoors use.
Heating means have been provided for use outdoors such as when camping, and as one example, liquid or solid hydrocarbon fuel is commonly used. Regarding special heating means, many are known, and among them there are heaters using the hydration reaction of calcium oxide or aluminum, and heaters using an exothermic substance formed by mixing aluminum powder with silicon powder, as disclosed in Japanese Patent Provisional Publication Showa 52-19358.
However, when using a liquid or solid fuel, in order to reduce the heating time, the device must be made quite large, thereby making it less handy to carry; in addition, use outdoors in a rain or strong wind is usually difficult. Regarding the heating method based on the hydration reaction, although it is more suited for use outdoors, the heating speed is relatively slow, and the amount of calories produced is extremely small in comparison with the weight of the pyrogen. Furthermore, regarding the exothermic substance disclosed in Japanese Patent Provisional Publication Showa 52-19358, given the nature of the pyrogen used, it requires firing by an electric heater or a lighter for a while in order to be ignited; thus the amount of calories needed for ignition is large, and ignition quality is poor.
Taking into consideration the foregoing problems, the present inventors have developed an instant heating device which provides a low-cost method of heating and which generates a large amount of calories and is easy to ignite. This device may be described as an instant heater and includes a pyrogen, which is a mixture of one or more kinds of metal oxide powder and one or more kinds of semi-metal powder; a firing agent which is a mixture of one or more kinds of metal oxide powder and one or more kinds of metal and semi-metal powder, the agent being in contact with the pyrogen and being easier to ignite than the pyrogen; and an igniter which is placed close to the firing agent and is used for igniting the firing agent, by mixing an oxidizing agent such as chlorate, perchlorate or nitrate with an inflammable material, or by sparks from a flint. The pyrogen, firing agent and igniter are stored in a metal container (an outer shell); a small hole or thin tube passes through the wall of the container; a string or thin wire is run from the igniter to the outside of the container through this small hole or thin tube; and ignition is realized by pulling or pushing this string or thin wire from outside of the container, thus heating the firing part and the exothermic part. Japanese Patent Application Showa 63-63524 discloses an arrangement of the foregoing character.
The above-described instant heater has sufficiently satisfied the desired aim, but nevertheless questions have arisen regarding the safety of the ignition device before the desired time of use. Since the exothermic substance which is provided inside the heater reaches fairly high temperatures (1000.degree. C. or more) when heated, if ignited mistakenly when not intended for use, it could be extremely dangerous. Therefore, an ignition device so structured that it could be ignited only when the heater is intended to be used, and which could not be ignited by simply pulling or pushing a string or wire for ignition, is highly desirable.
It is a general object of this invention to provide a highly safe ignition device for instant heaters.